We have continued our study of visual motion processing in the cerebral cortex. Our investigations concentrated on two areas of cortex that are largely devoted to motion processing, the middle temporal area (MT) and the medical superior temporal area (MST). In area MST we investigated the response of cells to motion of the visual background as the monkey made a pursuit eye movement. We could identify two types of cells. One type responded vigorously to large field stimulation and this response frequently was synergistic with the pursuit response. Another group of cells respond to small moving spots and are largely insensitive to motion of the background. In area MT, we have investigated changes in the receptive field size of cells adjacent to a region damaged by a neurotoxin that impairs the monkey's ability to generate a pursuit eye movement. We found that the receptive fields did not expand selectively to cover the area of the visual field previously covered by the cells damaged by the neurotoxin. Many cells did, however, show an expansion of their field size in all directions.